Performance recovery method for fuel cell stack

Abstract

The present disclosure relates to a method for restoring the performance of a fuel cell stack in a fuel cell system of a vehicle. The method includes: using a predetermined stack status judgment standard and based on information collected from the vehicle, determining whether the fuel cell stack is in a state where a stack performance recovery operation can be performed; determining whether the vehicle is in a state where the stack performance recovery operation can be performed based on operating information of the fuel cell system; and performing the stack performance recovery operation when it is determined that the fuel cell stack is in a state where the stack performance recovery operation can be performed and the vehicle is in a state where the stack performance recovery operation can be performed.

Description

Technical Field

[0001] The present disclosure relates to a method for recovering the performance of a fuel cell stack, and more particularly, to an operation control method of a fuel cell system capable of recovering the performance of a fuel cell stack to improve the durability of the fuel cell stack. Background Art

[0002] A fuel cell is a power generation device that converts the chemical energy in a fuel into electrical energy through an electrochemical reaction between the fuel gas and an oxidizing gas. Such fuel cells are widely used as power sources in industry, homes, and vehicles. Fuel cells can also be used to power small electrical and electronic products and portable devices.

[0003] Currently, polymer electrolyte membrane fuel cells (or proton exchange membrane fuel cells) (PEMFCs) with high power density are being most studied as fuel cells for vehicles. In polymer electrolyte membrane fuel cells, hydrogen is used as fuel gas, and oxygen or air containing oxygen is used as oxidizing gas.

[0004] A fuel cell comprises a plurality of cells in which a fuel gas and an oxidizing gas react with each other to generate electricity. Typically, the plurality of cells are stacked in a stack and connected in series to meet output requirements.

[0005] Fuel cells used in vehicles require high power output. Therefore, to meet this power demand, hundreds of individual cells, each generating electricity individually, are stacked together in a stack. This stack of connected cells is called a fuel cell stack.

[0006] Each unit cell of a polymer electrolyte membrane fuel cell includes: a membrane electrode assembly (MEA), which includes a polymer electrolyte membrane capable of moving hydrogen ions and a catalyst electrode layer integrally attached to the opposite surface of the polymer electrolyte membrane; a gas diffusion layer (GDL), which is used to supply reaction gases such as fuel gas and oxidizing gas to the membrane electrode assembly and transmit the generated electrical energy; a gasket, which is used to maintain the airtightness of the reaction gas and coolant; a fastening member, which is used to maintain an appropriate fastening pressure; and a separator plate (bipolar plate, BP) for moving the reaction gas and coolant.

[0007] The membrane electrode assembly includes a polymer electrolyte membrane capable of transferring hydrogen ions and electrode layers such as an anode and a cathode coated on opposite surfaces of the polymer electrolyte membrane with a catalyst for inducing a reaction between hydrogen as a fuel gas and air (or oxygen) as an oxidizing gas.

[0008] In each unit cell of the fuel cell, a gas diffusion layer for uniformly distributing the fuel gas and the oxidizing gas is stacked on the outside of the membrane electrode assembly, that is, on the outside of each of the anode and the cathode, and a separator for providing a channel for the flow of the reaction gas and the coolant and supplying the reaction gas to the gas diffusion layer is arranged on the outside of the gas diffusion layer.

[0009] In addition, a gasket for fluid sealing is provided between components constituting the unit cell. The gasket may be formed integrally with the membrane electrode assembly or the separator plate.

[0010] The above elements constitute a unit cell. A fuel cell stack is constructed by stacking multiple cells, then attaching end plates for supporting the cells to the outermost sides of the stack. With the cells stacked between the end plates, the end plates are fastened to the cells using fastening members.

[0011] A fuel cell system installed in a fuel cell vehicle includes, in addition to a fuel cell stack, a device for supplying a reaction gas to the fuel cell stack.

[0012] That is, the fuel cell system includes: a fuel cell stack, configured to generate electrical energy through an electrochemical reaction of a reaction gas; a hydrogen supply device, configured to supply hydrogen used as a fuel gas to the fuel cell stack; an air supply device, configured to supply air including oxygen used as an oxidizing gas to the fuel cell stack; a heat and water management system, configured to control the operating temperature of the fuel cell stack and perform heat and water management functions; and a fuel cell system controller, configured to control the overall operation of the fuel cell system.

[0013] In a conventional fuel cell system, the hydrogen supply device may include a hydrogen storage unit (hydrogen tank), a regulator, a hydrogen pressure control valve and a hydrogen recirculator, the air supply device may include a blower or air compressor and a humidifier, etc., and the heat and water management system may include a water collector, an electric water pump (coolant pump), a water tank and a radiator, etc.

[0014] High-pressure hydrogen supplied from the hydrogen storage unit of the hydrogen supply device is reduced in pressure by a regulator to a predetermined pressure before being supplied to the fuel cell stack. The reduced-pressure hydrogen is supplied to the fuel cell stack at a controlled pressure and supply volume according to the operating conditions of the fuel cell stack.

[0015] In addition, unreacted residual hydrogen in the fuel cell stack is discharged through the outlet of the anode (hydrogen electrode) of the stack or recirculated to the inlet of the anode of the stack through a hydrogen recirculator.

[0016] A hydrogen recycler is a device that can improve the reliability of hydrogen supply and the life of a fuel cell. There are various recycling methods, and a method using an ejector, a method using a blower, and a method using both an ejector and a blower are known.

[0017] The hydrogen recirculator recirculates unreacted hydrogen that is not used in the anode of the fuel cell stack to the anode (hydrogen electrode) of the stack through a recirculation pipe to reuse the hydrogen.

[0018] In addition, in fuel cells, the greater the amount of foreign matter, such as nitrogen, water, and steam, that migrates through the electrolyte membrane in the stack to the anode, the less hydrogen there is in the anode, thus reducing reaction efficiency. Therefore, a hydrogen purge valve installed in the stack anode exhaust line can be opened to purge hydrogen.

[0019] Meanwhile, the durable life of a fuel cell stack is a very important factor in ensuring the marketability of a fuel cell vehicle. Therefore, various efforts have been made to prevent and increase the durable life of the fuel cell stack, and various studies have been conducted on the causes of stack degradation.

[0020] Furthermore, in recent years, fuel cell systems have become increasingly common in commercial vehicles, such as buses and trucks, as well as automobiles. Consequently, control technologies that can improve the durability of fuel cell systems have become a growing focus. In particular, research has been actively conducted to minimize the degradation of fuel cell stacks within fuel cell systems.

[0021] In view of the durability of the fuel cell stack, stack degradation can be mainly classified into reversible degradation and irreversible degradation. This degradation occurs due to various reasons, and a representative cause of reversible degradation is the generation of platinum catalyst oxide (Pt-OH).

[0022] Platinum catalyst oxides act as a reversible degradation factor in the early stages of their generation. However, if the oxides continue to remain in the stack, they transform into irreversible degradation factors through unexpected chemical reactions, causing irreversible degradation of the stack's durability.

[0023] Therefore, it is necessary to remove the oxides to restore the performance of the fuel cell stack. To ensure the durability of the stack, a recovery operation is required to periodically remove the oxides that cause reversible degradation at appropriate times (minimizing the reduction in durability also leads to improved stack efficiency).

[0024] As a method for removing oxides to restore the performance of a fuel cell stack, a method of inducing a reduction reaction by stack potential fluctuation, ie, voltage sweeping, is well known.

[0025] In addition, it is advantageous to keep the exposure voltage low for a long time to effectively perform the stack performance recovery operation in the voltage sweep mode, and it is known that the improvement effect is significant in the case where voltage fluctuations are repeatedly caused.

[0026] However, when the stack performance recovery operation mode is applied to a vehicle, the following problems are encountered.

[0027] First, it is necessary to determine whether the vehicle is in a state suitable for performing a fuel cell stack performance recovery operation using a voltage sweep method. Fundamentally, due to the characteristics of a vehicle's fuel cell stack, the stack must output current at all times, depending on the driver's request. Therefore, in order to perform multiple voltage sweeps while meeting these requirements, accurate criteria are required to ensure the timing of the stack performance recovery operation. This determination must take into account both the vehicle's and the fuel cell stack's conditions.

[0028] Furthermore, in the absence of a load, it is difficult to induce voltage fluctuations, and even when voltage is generated, it takes a long time to discharge (lower the voltage). Therefore, a method for quickly and efficiently inducing voltage fluctuations is needed.

[0029] Furthermore, to maximize the durability improvement effect of the recovery operation, the fuel cell stack must be maintained at a low voltage for an extended period of time. Furthermore, it is necessary to perform the recovery operation repeatedly in a low voltage state. However, if the recovery operation is not completed due to driver input requirements or vehicle conditions, it is necessary to identify this and reflect this in the next recovery operation to maximize the effectiveness of the recovery operation.

[0030] The information disclosed in the above Background section is for assisting understanding of the background of the present disclosure and should not be considered as an admission that this information constitutes any part of the prior art. Summary of the Invention

[0031] The present disclosure is proposed to solve the above-mentioned problems related to the prior art, and the purpose of the present disclosure is to provide a performance recovery method for a fuel cell stack, which accurately judges whether the stack is in a state where the stack performance recovery operation can be performed and whether the vehicle is in a state where the stack performance recovery operation can be performed, thereby appropriately ensuring the performance recovery operation time during vehicle driving and more effectively performing voltage scanning and stack performance recovery.

[0032] In one aspect of the present disclosure, a method for recovering the performance of a fuel cell stack in a fuel cell system of a vehicle may include: judging, by a controller, whether the fuel cell stack is in a state where a stack performance recovery operation can be performed based on information collected from the vehicle using a predetermined stack status judgment standard; judging, by the controller, whether the vehicle is in a state where a stack performance recovery operation can be performed based on operating information of the fuel cell system; and performing a stack performance recovery operation by the controller when it is judged that the fuel cell stack is in a state where a stack performance recovery operation can be performed and the vehicle is in a state where a stack performance recovery operation can be performed.

[0033] Other aspects and preferred embodiments of the disclosure are discussed below.

[0034] It will be understood that the term "vehicle" or "vehicular" or other similar terms as used herein includes general motor vehicles, such as passenger cars including sport utility vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft including various ships and boats, aircraft, etc., and includes hybrid vehicles, electric vehicles, plug-in hybrid vehicles, hydrogen-powered vehicles, and other alternative fuel (e.g., fuels derived from resources other than petroleum) vehicles. As referred to herein, a hybrid vehicle is a vehicle having two or more power sources, such as gasoline-powered and electric-powered vehicles.

[0035] The above and other features of the present disclosure are discussed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The above and other features of the present disclosure will now be described in detail with reference to certain exemplary embodiments thereof as shown in the accompanying drawings, which are given hereinafter by way of illustration only and thus do not limit the present disclosure, and in which:

[0037] Figure 1 is a view schematically showing main components of a power grid structure of a fuel cell system that performs a fuel cell stack performance recovery operation according to an aspect of the present disclosure;

[0038] Figure 2 is a flow chart illustrating an overall process for fuel cell stack performance recovery according to one aspect of the present disclosure;

[0039] Figure 3 is a flowchart illustrating a method of determining whether a heap is in a state requiring a heap performance recovery operation according to an aspect of the present disclosure;

[0040] Figure 4 is a flowchart illustrating a method for confirming the number of fuel cell stop entry times according to an aspect of the present disclosure;

[0041] Figure 5is a flowchart illustrating a method of determining whether a vehicle is in a state where a stack performance recovery operation can be performed according to an aspect of the present disclosure;

[0042] Figure 6 is a flowchart illustrating a method of determining whether a heap performance recovery operation has been completed and changing a heap status determination criterion when not completed according to an aspect of the present disclosure; and

[0043] Figure 7 is a diagram illustrating an example of changing a stack state judgment criterion according to an aspect of the present disclosure.

[0044] It should be understood that the drawings are not necessarily drawn to scale, but rather present a somewhat simplified representation of various preferred features illustrating the basic principles of the present disclosure. The specific design features of the present disclosure disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes, will be determined in part by the specific intended application and use environment.

[0045] In the drawings, reference numbers refer to the same or equivalent parts of the present disclosure throughout the various figures. DETAILED DESCRIPTION

[0046] Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the present disclosure. However, the present disclosure is not limited to the embodiments disclosed herein and can be implemented in various different forms.

[0047] Unless otherwise stated, the terms “include” and “comprising” described herein should not be interpreted as excluding other elements but rather as further including these other elements.

[0048] First, the present disclosure relates to a fuel cell stack performance recovery method capable of improving the durability of a fuel cell stack by preventing irreversible degradation of a fuel cell stack of a fuel cell system installed in a fuel cell vehicle.

[0049] According to one aspect of the present disclosure, a logic is disclosed for determining whether a current vehicle is in a state where an operation to restore the performance of a fuel cell stack can be performed using information such as an integrated value of stack current, accumulated driving distance, number of fuel cell stop entries, battery state of charge (SOC), battery dischargeable power, and stack required output.

[0050] According to one aspect of the present disclosure, a method for efficiently inducing voltage fluctuation using an air compressor and a cathode oxygen depletion (COD) heater is disclosed. To achieve electrical isolation between a high-voltage battery and the COD heater during voltage fluctuation, a main relay is also controlled.

[0051] According to an aspect of the present disclosure, a time when a recovery operation has not been completed due to a driver output request or a condition of a vehicle is determined and reflected in the next stack performance recovery operation to maximize the effect of the stack performance recovery operation.

[0052] Figure 1 is a view schematically illustrating main components of a power grid structure of a fuel cell system that performs a fuel cell stack performance recovery operation according to an aspect of the present disclosure.

[0053] Reference Figure 1 The fuel cell system installed in a fuel cell vehicle includes: a fuel cell stack 10, serving as a main power source (electric power source) of the vehicle; a high-voltage battery (main battery) 16, serving as an auxiliary power source of the vehicle; a bidirectional high-voltage DC / DC converter (BHDC) 15, connected to the high-voltage battery 16 to control the output of the high-voltage battery 16; an inverter 12, connected to the fuel cell stack 10 and a main bus terminal serving as an output side of the high-voltage battery 16; a drive motor 13, connected to the inverter 12; and a controller 17, configured to control the operation of the fuel cell system.

[0054] The controller 17 of the fuel cell system according to the exemplary embodiment of the present disclosure may be a processor (e.g., a computer, a microprocessor, a CPU, an ASIC, a circuit system, a logic circuit, etc.). The controller 17 may be implemented by a non-transitory memory storing, for example, a program, a software instruction reproduction algorithm, etc., that controls the operation of the various components of the fuel cell vehicle when executed, and a processor configured to execute the program, the software instruction reproduction algorithm, etc. Here, the memory and the processor may be implemented as separate semiconductor circuits. Alternatively, the memory and the processor may be implemented as a single integrated semiconductor circuit. The processor may be embodied as one or more processors.

[0055] exist Figure 1 , reference numeral 14 denotes a COD heater 14 connected to a main bus terminal to be operated by the output (output current) of the fuel cell stack 10 to heat the stack coolant, and reference numeral 18 denotes an air compressor configured to supply air serving as an oxidizing gas to the fuel cell stack 10. These are also components of the fuel cell system.

[0056] According to an aspect of the present disclosure, the COD heater 14 and the air compressor 18 may be used as means for sweeping the stack voltage (to cause the voltage to fluctuate) during operation to restore the performance of the fuel cell stack 10 .

[0057] like Figure 1As shown, in the fuel cell system, a fuel cell stack 10 as a main power source and a high-voltage battery 16 as an auxiliary power source are connected in parallel to an inverter 12 / drive motor 13 as a load in the system through main bus terminals.

[0058] In addition, the converter 15 connected to the high-voltage battery 16, that is, the bidirectional high-voltage DC / DC converter (BHDC) is connected to the main bus terminal which is the output side of the fuel cell stack 10, so that the output of the fuel cell stack 10 and the high-voltage battery 16 can be controlled by controlling the voltage of the bidirectional high-voltage DC / DC converter 15 (the output voltage output to the main bus terminal).

[0059] In addition, a main relay 11 configured to selectively connect the fuel cell stack to a main bus terminal is installed on the output side of the fuel cell stack 10 .

[0060] The drive motor 13 is a motor configured to drive the vehicle. The inverter 12 is connected to the output side of the fuel cell stack 10 and the high-voltage battery 16 via main bus terminals, and performs phase conversion on the power supplied from the fuel cell stack 10 and / or the high-voltage battery 16 to drive the drive motor 13.

[0061] According to one aspect of the present disclosure, the controller 17 controls the overall operation of the components of the fuel cell system. For example, the controller 17 controls the operations of the main relay 11, the inverter 12, the COD heater 14, the converter 15, and the air compressor 18.

[0062] According to one aspect of the present disclosure, a stack performance recovery method uses a method for controlling an electrical load device connected to a fuel cell stack to receive power from the fuel cell stack and thereby consume power from the fuel cell stack. Specifically, the method involves controlling the operation of the electrical load device, which is configured to act as an electrical load relative to the fuel cell stack, to sweep the stack voltage. In this case, the operation of the electrical load device is controlled by a controller 17.

[0063] That is, when the controller 17 outputs a control signal for scanning the stack voltage during the stack performance recovery operation, the operation of the electric load device is controlled according to the control signal output by the controller 17 to scan the stack voltage.

[0064] As described above, in the present disclosure, the COD heater 14 and the air compressor 18 may serve as electric load devices for sweeping the stack voltage, and the controller 17 controls operations of the COD heater 14 and the air compressor 18 such that the stack voltage is swept during the stack performance recovery operation.

[0065] The heap performance recovery operation will be described in detail below.

[0066] Figure 21 is a flowchart illustrating an overall process for fuel cell stack performance recovery according to an aspect of the present disclosure, wherein a process for controlling a fuel cell system for stack performance recovery operation according to an aspect of the present disclosure is illustrated.

[0067] The fuel cell stack performance recovery operation according to an aspect of the present disclosure is performed by the controller 17 based on information collected from the vehicle, and the controller 17 may be a fuel cell system controller configured to control the overall operation of the fuel cell system.

[0068] According to one aspect of the present disclosure, the controller 17 is configured to execute Figure 2 The entire process for fuel cell stack performance recovery shown and executed Figures 3 to 6 The detailed logic of each process is shown in .

[0069] like Figure 2 As shown, the performance recovery method of a fuel cell stack according to one aspect of the present disclosure includes the following processes: the controller 17 determines whether the stack is in a state where a stack performance recovery operation can be performed (S10); the controller 17 determines whether the vehicle is in a state where a stack performance recovery operation can be performed (S30); and when each of the stack and the vehicle is in a state where a stack performance recovery operation can be performed, the controller 17 performs the stack performance recovery operation (S40).

[0070] In addition, the performance recovery method of the fuel cell stack according to one aspect of the present disclosure may further include the following process: after the process of determining whether the stack is in a state where the stack performance recovery operation can be performed, and before the process of determining whether the vehicle is in a state where the stack performance recovery operation can be performed, the controller 17 confirms the number of fuel cell stop entry times (S20).

[0071] In this case, the controller 17 executes the subsequent process, ie, executes the stack performance recovery operation, only when each of the stack and the vehicle is in a state where the stack performance recovery operation can be executed and the conditions related to the number of fuel cell stop entries are satisfied.

[0072] In addition, the performance recovery method of the fuel cell stack according to one aspect of the present disclosure may further include the following processes: the controller 17 determines whether the stack performance recovery operation has been completed (S50); and when the stack performance recovery operation has not been completed, the controller 17 changes the stack status judgment standard (S60).

[0073] According to an aspect of the present disclosure, when the controller 17 determines that the stack performance recovery operation has been completed or the stack state judgment criterion is changed, the controller 17 ends the stack performance recovery operation ( S70 ).

[0074] In the following description, a stack refers to the fuel cell stack 10 of a fuel cell system installed in a fuel cell vehicle, a fuel cell in fuel cell stoppage refers to the fuel cell stack, and recovery of stack performance refers to recovery of the fuel cell stack performance.

[0075] In addition, the stack performance recovery operation may refer to an operation of the fuel cell system to recover the performance of the fuel cell stack, and control of the operation of the fuel cell system for the stack performance recovery is performed by the controller 17 .

[0076] In addition, according to one aspect of the present disclosure, voltage sweep refers to sweeping the voltage of the fuel cell stack 10 , and voltage sweep and voltage fluctuation may be understood to have the same meaning.

[0077] Figure 3 This invention is a flowchart illustrating a method for determining whether a heap is in a state where a heap performance recovery operation can be performed according to one aspect of the present disclosure. The heap being in a state where a heap performance recovery operation can be performed may mean that the heap is in a state where a heap performance recovery operation is required. In order to initiate a heap performance recovery operation, it is necessary to first determine whether the heap is in a state where a heap performance recovery operation is required.

[0078] According to one aspect of the present disclosure, the stack performance recovery operation mode is a mode of recovering the reversible degradation of the fuel cell stack 10 caused by catalyst oxides, and the more times the fuel cell stack 10 is used, the more catalyst oxides are generated. Therefore, in the stack status judgment standard, how many times the stack has been used is important.

[0079] Therefore, according to an aspect of the present disclosure, the state of the stack for entering the stack performance recovery operation is judged based on the integrated value of the stack current or the cumulative travel distance of the vehicle traveling with the stack output above a predetermined level.

[0080] At this time, during the operation of the fuel cell system, the controller 17 calculates and uses an integrated value of the stack current above the lower limit value I1. Figure 3 In FIG. 1 , I1 represents the lower limit value, which is a value preset in the controller 17 to remove the noise value of the stack current and can be set to a smaller value capable of distinguishing the noise value.

[0081] As described above, according to one aspect of the present disclosure, when calculating the integrated value of the stack current, the lower limit value I1 of the integrated stack current is applied to remove noise values, and the integrated value of the stack current is calculated when the stack output, i.e., the stack current, is greater than the lower limit value I1 ( S11 and S13 ).

[0082] When calculating the integrated value of the stack current, the controller 17 is set to integrate only the stack current (stack output) that is equal to or greater than the lower limit value I1 .

[0083] In addition, when calculating the cumulative running distance, the controller 17 cumulatively calculates the running distance of the vehicle when the stack output is greater than or equal to a predetermined first output reference value I2 during the running of the vehicle and the operation of the fuel cell system (S12 and S14). Here, the stack output may be a stack current.

[0084] That is, the cumulative running distance of the vehicle running with the stack current greater than the first output reference value I2 is calculated. Figure 3 , I2 represents a first output reference value, which is a value for cumulatively calculating a travel distance of a vehicle when the stack 10 is used, and may be set to a value capable of representing the stack output.

[0085] According to one aspect of the present disclosure, as described above, only the running distance of the vehicle when the stack current is greater than the first output reference value I2 is accumulated to calculate the cumulative running distance. Figure 3 In the embodiment, the lower limit value I1 and the first output reference value I2 may both be values ​​set for the stack current.

[0086] According to one aspect of the present disclosure, at least one of an integrated value of the stack current or a cumulative driving distance may be utilized. When the integrated value of the stack current is greater than a predetermined current integrated reference value Q1 or the cumulative driving distance is greater than a predetermined distance reference value D1, the controller 17 determines that the stack is in a state requiring a stack performance recovery operation (S15).

[0087] When it is determined that the stack is in a state where a stack performance recovery operation needs to be performed, the controller 17 resets the integral value of the stack current or the accumulated driving distance (S16) and performs a subsequent process for stack performance recovery, i.e., a process for confirming the number of fuel cell stop entries (S20).

[0088] exist Figure 3 In the figure, Q1 represents the current integral reference value, and D1 represents the distance reference value. Both Q1 and D1 are stack status judgment criteria for judging the number of times the stack has been used, and the entry cycle and execution cycle of the stack performance recovery operation are judged based on these values.

[0089] Several technologies have been proposed to monitor the status of the stack 10 , and most utilize methods that estimate the gradient of the stack current-voltage characteristic curve. However, to estimate reliable values ​​using this method, the stack must operate in various current regions.

[0090] However, in a case where the vehicle is driven mainly in the local current region according to the driver's driving style, it is impossible to judge whether the stack performance recovery operation needs to be performed.

[0091] In actual commercial vehicles, sudden changes in stack output can reduce vehicle durability and, due to the large amount of heat generated within the vehicle, can cause thermal shock. Consequently, a fixed-point stack operation strategy is often employed. Consequently, estimating the gradient of the stack current-voltage characteristic curve is not suitable for determining stack status.

[0092] Figure 4 1 is a flowchart illustrating a method for confirming the number of times a fuel cell stop (Fuel Cell Stop) is entered according to an aspect of the present disclosure. According to an aspect of the present disclosure, as described above, a method for a performance recovery operation through stack voltage scanning is adopted.

[0093] However, during the operation of a fuel cell vehicle, a fuel cell stop state may occur, and the stack voltage may drop to a low potential due to natural discharge during the fuel cell stop state. As described above, when the stack voltage drops due to fuel cell stop and a voltage change occurs above a predetermined level, the stack performance recovery effect is achieved.

[0094] Therefore, according to one aspect of the present disclosure, the controller 17 can be set to repeatedly cause the fuel cell stop state to occur within a predetermined time during the operation of the fuel cell system, and thus when the stack voltage drops below the predetermined voltage reference value V1 a number of times equal to or greater than a first predetermined number C1, it is judged that stack performance recovery operation is not required.

[0095] If this is not the case, that is, Figure 4 In step S21, when the number of times the stack voltage drops below the predetermined voltage reference value V1 when the fuel cell stops within the predetermined time is less than the first predetermined number C1, after the predetermined time, the controller 17 resets the number of times the stack voltage is equal to or less than the voltage reference value V1 (S22), and executes a subsequent process for stack performance recovery, that is, a process for determining whether the vehicle is in a state where it can enter a stack performance recovery operation (S30).

[0096] exist Figure 4 In FIG. 5 , V1 represents a voltage reference value for specifying a voltage level capable of achieving the effect of the stack performance recovery operation due to the stop of the fuel cell, and may be set to a low voltage capable of achieving the effect of the stack performance recovery operation.

[0097] According to one aspect of the present disclosure, when the stack voltage drops to a voltage reference value V1 while the fuel cell is stopped, a stack performance recovery operation can be performed. Specifically, when the stack voltage drops below the voltage reference value V1 for less than a first predetermined number of times C1 while the fuel cell is stopped, subsequent processes for stack performance recovery are continued.

[0098] exist Figure 4, C1 represents the minimum number of times required to achieve the effect of the stack performance recovery operation, i.e., the first predetermined number C1. If the number of times the stack voltage drops below the voltage reference value V1 within the predetermined time is less than the first predetermined number C1, the controller 17 determines that the effect of the stack performance recovery operation cannot be achieved and executes a subsequent process for stack performance recovery.

[0099] Typically, the fuel cell stops when there is no stack output. Therefore, in the previous stack status confirmation process, when the integrated value of the stack current is greater than the current integrated reference value Q1 or the accumulated driving distance is greater than the distance reference value D1, the fuel cell stop state can be avoided to some extent based on the stack output conditions at that time.

[0100] In addition, it takes a long time for the stack voltage to drop below the voltage reference value V1 simply due to the natural voltage drop when the fuel cell is stopped. Therefore, the possibility of the stack voltage dropping below the voltage reference value V1 occurring multiple times within the predetermined time when the fuel cell is stopped is not high.

[0101] Therefore, the process of confirming the number of fuel cell stop entry times is not an essential process that must be performed during the operation of recovering the performance of the fuel cell stack.

[0102] That is, when the controller 17 determines that the stack 10 is in a state requiring stack performance recovery, the logic can be configured to determine whether the vehicle is in a state suitable for stack performance recovery after confirming the number of fuel cell stop entry attempts. Alternatively, the controller 17 can confirm the vehicle state immediately after confirming the stack state, without executing the process of confirming the number of fuel cell stop entry attempts.

[0103] Figure 5 is a flowchart showing a method for determining whether a vehicle is in a state where a stack performance recovery operation can be performed according to one aspect of the present disclosure. According to one aspect of the present disclosure, the controller 17 is configured to Figure 5 The logic shown in is used to confirm whether the vehicle is in a state where the stack performance recovery operation can be performed.

[0104] That is, when it is determined in process S10 that the stack is in a state where the performance recovery operation needs to be performed, and in process S20 the number of fuel cell stop entry times is confirmed and the stack is in a state where the stack performance recovery operation needs to be performed, the controller 17 determines in the subsequent process S30 whether the vehicle is in a state where the stack performance recovery operation can be performed (see Figure 2 ).

[0105] Since the vehicle basically has to produce the output desired by the driver, it is confirmed whether the vehicle can travel without the output of the stack 10 , and the stack performance recovery operation must be performed in a subsequent process when the vehicle can travel without the stack output.

[0106] In this process, the controller 17 confirms whether the vehicle can travel without the output of the stack 10. If the vehicle can travel without the output of the stack 10, the controller 17 determines that the vehicle is in a state where the stack performance recovery operation can be performed.

[0107] Reference Figure 5 , showing detailed steps of a process for determining whether a vehicle is in a state where a stack performance recovery operation can be performed.

[0108] like Figure 5 As shown, the controller 17 determines whether the vehicle is running in a key-on state (S31), and when the vehicle is running, compares the SOC of the high-voltage battery (main battery) 16 connected to the drive motor to supply power to the drive motor with a predetermined first SOC reference value S1 (S32).

[0109] Here, when the SOC of the high voltage battery 16 is equal to or greater than the first SOC reference value S1 , the controller 17 compares the dischargeable power of the high voltage battery 16 with a predetermined first power reference value W1 ( S33 ).

[0110] Subsequently, when the dischargeable power of the high-voltage battery 16 is equal to or greater than the first power reference value W1, the controller 17 compares the current stack required output determined when the fuel cell system is operating with a predetermined second output reference value I3 (S34). Subsequently, when the stack required output is less than the second output reference value I3, the controller 17 determines that the vehicle is in a state where the stack performance recovery operation can be performed even while the vehicle is traveling.

[0111] That is, when the conditions that the vehicle will travel in the starting state, the SOC of the high-voltage battery 16 is equal to or greater than the first SOC reference value S1, the dischargeable power of the high-voltage battery 16 is equal to or greater than the first power reference value W1, and the stack required output is less than the second output reference value I3 are all met, the controller 17 determines that the vehicle is in a state where the stack performance recovery operation can be performed even if the vehicle is driving.

[0112] On the other hand, when the vehicle is in a key-off state rather than a driving state, the controller 17 compares the SOC of the high-voltage battery 16 with the second SOC reference value S2 (S35), and when the SOC of the high-voltage battery 16 is equal to or greater than the second SOC reference value S2, it is judged that the vehicle is in a state where the stack performance recovery operation can be performed.

[0113] As described above, the controller 17 confirms whether the vehicle is driving, whether the vehicle is in the on / off state, the SOC of the high-voltage battery (main battery) 16, the dischargeable power of the high-voltage battery 16, and the stack required output to determine whether the vehicle is in a state where the stack performance recovery operation can be performed.

[0114] Here, the stack required output, as a value determined by the operation information of the fuel cell system, may refer to a current value required by the stack. A method of determining the current stack required output based on the operation information of the fuel cell system is known in the art, and a detailed description thereof will be omitted.

[0115] exist Figure 5 When the vehicle is running in the start state, the controller 17 determines that the stack performance recovery operation can be performed only when the SOC of the high voltage battery 16 is equal to or greater than the first SOC reference value S1.

[0116] Whether the SOC of the high voltage battery 16 is equal to or greater than the first SOC reference value S1 is information about whether the vehicle can travel using the high voltage battery 16 without the output of the stack 10. The higher the SOC of the high voltage battery 16, the longer the performance recovery operation time.

[0117] However, if the first SOC reference value S1 is set to a value that is too high to be reached during driving, the stack performance recovery operation may not be performed, so the first SOC reference value S1 needs to be set to an appropriate value (eg, S1 = 60%).

[0118] exist Figure 5 , W1 represents a first power reference value, which is a value set in the controller 17 to determine whether the vehicle can travel using the high-voltage battery 16 and can be set to a value equal to or greater than the average required output of the drive motor 13.

[0119] According to an aspect of the present disclosure, when the dischargeable power of the high voltage battery 16 is equal to or greater than the first power reference value W1 , the controller 17 determines that the vehicle can travel using the high voltage battery 16 .

[0120] exist Figure 5 In the figure, I3 represents a second output reference value, which is compared with the stack required output and is set to a low value in the controller 17 to determine that the output required by the vehicle can be provided by the high voltage battery 16 and the stack required output is very small (for example, the second output reference value = 5A).

[0121] exist Figure 5When the vehicle is not traveling and is in the ignition-off state, if the SOC of the high-voltage battery 16 is equal to or greater than the second SOC reference value S2, the controller 17 determines that the stack performance recovery operation can be performed.

[0122] When the vehicle is in the off state and is not driving, it is sufficient to ensure the low SOC of the battery required to perform stack performance recovery operations (air compressor on / off control, etc.), so the second SOC reference value S2 can be set to a value lower than the first SOC reference value S1 (for example, S2 = 25%).

[0123] Figure 6 is a flowchart illustrating a method of determining whether a heap performance recovery operation has been completed and changing a heap status determination criterion when not completed according to an aspect of the present disclosure.

[0124] like Figure 1 As shown, when each of the stack and the vehicle is in a state where the stack performance recovery operation can be performed and the conditions related to the number of fuel cell stop entries are satisfied, the controller 17 executes a predetermined stack performance recovery operation process.

[0125] According to an aspect of the present disclosure, stack performance recovery may be achieved by operating the COD heater 14 and simultaneously repeatedly controlling on / off of the air compressor 18 to sweep the stack voltage.

[0126] That is, when the stack is in a state where the stack performance recovery operation can be performed, when the result of confirming the number of fuel cell stop entry times meets the predetermined condition, and when the vehicle is in a state where the stack performance recovery operation can be performed, the controller 17 performs Figure 6 Heap performance recovery operation shown.

[0127] During the stack performance recovery operation, the vehicle driving mode is first switched to the high-voltage battery driving mode (stack output for driving is limited) (S41). The high-voltage battery driving mode is a mode in which the vehicle drives by discharging the battery, and is a mode in which the drive motor 13 is driven by the charged power of the high-voltage battery 16 rather than the generated power of the fuel cell stack 10, so that the vehicle drives.

[0128] Subsequently, the controller 17 turns off the main relay 11 of the fuel cell system ( S42 ), turns on the COD heater 14 ( S43 ), performs cooling control on the COD heater ( S44 ), and controls the hydrogen supply pressure to be equal to or higher than a predetermined target pressure H1 ( S45 ).

[0129] At this time, when the main relay is turned off by the controller 17 , the electric path formed from the high voltage battery 16 when the COD heater is turned on may be blocked.

[0130] As described above, when the COD heater 14 is turned on while the stack performance recovery operation is performed in a state where the main relay 11 is off, the COD heater 14 may function as an electric load that consumes stack power.

[0131] In addition, the cooling control process of the COD heater 14 may be a process of controlling the temperature of the COD heater to prevent the COD heater from overheating. While the COD heater 14 is being cooled, the controller 17 operates a coolant pump (not shown) at a speed greater than or equal to a predetermined RPM and controls the operation of the coolant bypass valve to maintain its opening toward the COD heater at a predetermined level.

[0132] At this time, based on the heat generation capacity of the COD heater 14 , the rotation speed of the coolant pump and the opening degree of the coolant bypass valve toward the COD heater are set to prevent the COD heater from overheating when the stack performance recovery operation is performed.

[0133] In addition, the controller 17 controls the hydrogen pressure control valve (not shown) and the like to maintain the pressure of hydrogen supplied to the fuel cell stack 10, that is, the hydrogen supply pressure, above the predetermined target pressure H1. During the stack performance recovery operation, it is sufficient to maintain the hydrogen supply pressure at a pressure required to generate the stack voltage and the current due to the operation of the COD heater 14 as a load.

[0134] Therefore, the target pressure H1 during the stack performance recovery operation may be set to a value of the basic target pressure level in normal operation (eg, target pressure = 130 kPa).

[0135] In addition, the controller 17 scans the stack voltage to recover the stack performance while the cooling control of the COD heater 14 is being executed. To scan the stack voltage, the air compressor 18 is on / off controlled (S46).

[0136] That is, the controller 17 controls the operation of the air compressor 18 so that the air compressor 18 is alternately turned on and off. When the air compressor is on, it is sufficient to supply only enough air to generate voltage to the stack 10, so the air compressor 18 is controlled to a basic operating level during normal operation.

[0137] In addition, when the controller 17 controls the operation of the air compressor 18 so that the air compressor 18 is alternately turned on and off, the holding time for each of the on and off operations can be applied separately. In order to maximize the effect of the stack performance recovery operation, the time for maintaining the low potential is important, so the off holding time can be set to be longer than the on holding time.

[0138] When repeatedly controlling the air compressor 18 to turn on and off, the controller 17 counts the number of times the on / off control of the air compressor is performed. Figure 6 When the number of executions of the on / off control of the air compressor counted in step S52 reaches the second predetermined number C2, the controller 17 determines that the stack performance recovery operation has been completed.

[0139] In addition, while repeatedly controlling the air compressor 18 to turn on and off, the controller 17 determines whether a stack performance recovery operation interruption condition is satisfied based on operation information of the fuel cell system collected from the vehicle ( S51 ).

[0140] When the heap performance recovery operation interruption condition is satisfied, it is determined whether the heap performance recovery operation has been completed (S52). Even if the heap performance recovery operation interruption condition is satisfied in step S51 and the heap performance recovery operation must be interrupted, if it is determined in step S52 that the heap performance recovery operation has not been completed, the controller 17 ends the heap performance recovery operation after changing the heap status judgment standard in step S60 (S70).

[0141] On the other hand, when it is determined in step S51 that the stack performance recovery operation interruption condition is met, and when it is determined in step S52 that the stack performance recovery operation has been completed, the controller 17 immediately ends the stack performance recovery operation (S70) without changing the stacking state judgment standard.

[0142] If it is determined in step S51 that the stack performance recovery operation interruption condition is not satisfied during the stack performance recovery operation, the controller 17 maintains the stack performance recovery operation until the stack performance recovery operation is completed ("No" in step S53). At this time, the controller 17 counts the number of executions of the on / off control of the air compressor 18, and when the number of executions of the on / off control of the air compressor 18 counted in step S53 reaches the second predetermined number C2, the controller 17 determines that the stack performance recovery operation has been completed and ends the stack performance recovery operation (S70).

[0143] According to one aspect of the present disclosure, the stack performance recovery operation interruption condition may be a condition that the stack required output during the stack performance recovery operation is equal to or greater than a third output reference value, a condition that the SOC of the high-voltage battery 16 is less than a third SOC reference value, or a condition that the dischargeable power of the high-voltage battery 16 is less than a second power reference value.

[0144] That is, according to one aspect of the present disclosure, during a stack performance recovery operation in which the air compressor 18 is repeatedly controlled to turn on and off to scan the stack voltage, the controller 17 compares the stack required output with a third output reference value, compares the SOC of the high-voltage battery 16 with a third SOC reference value, and compares the dischargeable power of the high-voltage battery 16 with a second power reference value. When the stack required output is equal to or greater than the third output reference value, the SOC of the high-voltage battery 16 is less than the third SOC reference value, or the dischargeable power of the high-voltage battery 16 is less than the second power reference value, the controller 17 determines that a stack performance recovery operation interruption condition is satisfied.

[0145] As described above, when it is determined that the stack performance recovery operation interruption condition is satisfied during the stack performance recovery operation, the controller 17 terminates the stack performance recovery operation. At this time, if the number of executions of the on / off control of the air compressor 18 after the start of the stack performance recovery operation is less than the second predetermined number C2, the controller 17 determines that the stack performance recovery operation has not been completed, changes the stack state determination criteria for the next stack performance recovery operation (S60), and terminates the stack performance recovery operation (S70).

[0146] However, when the stack performance recovery operation interruption condition is met, when the number of executions of the on / off control of the air compressor 18 has reached the second predetermined number C2, the controller 17 determines that the stack performance recovery operation has been completed and immediately ends the stack performance recovery operation without changing the stack status judgment standard (S70).

[0147] In the stack performance recovery operation interruption condition, the third output reference value is a reference value for judging the situation where the stack output is required due to the stack performance recovery operation, and can be set in the controller 17 to be higher than the value in the Figure 5 The value of the second output reference value I3 in step S34 of the vehicle state judgment process.

[0148] In the stack performance recovery operation interruption condition, the third SOC reference value is a reference value for judging that the SOC of the high-voltage battery 16 is excessively reduced. When the stack performance recovery operation is continuously performed and the SOC of the high-voltage battery 16 is excessively reduced as a result, normal operation in the high-voltage battery driving mode may be impossible.

[0149] Therefore, when the SOC of the high voltage battery 16 is less than the third SOC reference value, the controller 17 determines that the stack performance recovery operation interruption condition is satisfied and ends the stack performance recovery operation to prevent normal operation from being impossible in the high voltage battery driving mode.

[0150] According to one aspect of the present disclosure, the third SOC reference value S3 must be set in the controller 17 to be lower than Figure 5The first SOC reference value S1 in step S32 of the vehicle state judgment process may be set to the same as that in Figure 5 The value is the same as the second SOC reference value S2 in step S35 of the vehicle state judgment process, or a value smaller than the second SOC reference value S2 by a predetermined value or less (for example, S2 and S3 = 25%).

[0151] In the battery stack performance recovery operation interruption condition, the second power reference value is a reference value for judging that the dischargeable power of the high-voltage battery 16 is excessively reduced. When the dischargeable power of the high-voltage battery 16 is excessively reduced, normal operation in the high-voltage battery travel mode may be impossible.

[0152] Therefore, when the dischargeable power of the high-voltage battery 16 is less than the second power reference value, the controller 17 determines that the stack performance recovery operation interruption condition is met and ends the stack performance recovery operation to prevent normal operation from being impossible in the high-voltage battery driving mode.

[0153] According to one aspect of the present disclosure, the dischargeable power of the high-voltage battery 16 is changeable according to the temperature and voltage of the high-voltage battery 16, etc., and the controller 17 can determine the dischargeable power of the high-voltage battery 16 based on information about the temperature and voltage of the high-voltage battery 16 collected by a detection element such as a sensor.

[0154] A method of determining the dischargeable power of the high-voltage battery 16 is known in the art, and a detailed description thereof will be omitted.

[0155] According to one aspect of the present disclosure, the second power reference value may be set in the controller 17 to be lower than Figure 5 The value of the first electric power reference value W1 in step S33 of the vehicle state judgment process.

[0156] According to one aspect of the present disclosure, the number of executions of the on / off control of the air compressor can be defined in such a manner that when the on and off of the air compressor 18 are maintained for their respective predetermined holding times once, the number of executions of the on / off control of the air compressor is 1.

[0157] When the second predetermined number C2 is reached, the controller 17 may determine that the stack performance recovery operation is complete.

[0158] Ending the heap performance recovery operation means returning to the state before the heap performance recovery operation was performed. Figure 6 All steps S41 to S46 that started when the stack performance recovery operation is completed are completed, and the normal driving mode is switched to.

[0159] At the same time, even if the predetermined stack performance recovery operation interruption condition is met and the stack performance recovery operation must therefore be terminated, when the number of executions of the on / off control of the air compressor 18 does not reach the second predetermined number C2, that is, when the stack performance recovery operation has not been completed, the change of the stack status judgment criterion in step S60 is executed.

[0160] At this time, when the heap performance recovery operation has not yet been completed, the heap state judgment standard is changed so that the next heap performance recovery operation is performed earlier than this time. Here, the heap state judgment standard can be used as the Figure 3 The current integral reference value Q1 as a standard for judging the integral value of the stack current in the stack state judgment process, the distance reference value D1 as a standard for judging the accumulated running distance, or both the current integral reference value Q1 and the distance reference value D1.

[0161] Figure 7 is a diagram illustrating an example of changing a stack state judgment criterion according to an aspect of the present disclosure. Figure 7 In the figure, the minimum reference may be the lower limit value of the current integral reference value Q1 or the lower limit value of the distance reference value D1.

[0162] According to one aspect of the present disclosure, when the number of executions of the on / off control of the air compressor 18 has not reached the second predetermined number C2 even though the stack performance recovery operation interruption condition is met, the reference values ​​Q1 and D1 can be reduced by a predetermined value so that the next stack performance recovery operation is performed earlier than this time.

[0163] According to one aspect of the present disclosure, if the reference value used for heap status judgment is set to a very small value, the recovery operation may be entered too frequently after the heap performance recovery operation has not yet been completed. Therefore, an appropriate reference value above a predetermined level is set through preliminary testing and evaluation.

[0164] The two reference values ​​Q1 and D1 may be set to different values. Figure 7 The curve diagram shows two examples of reference values.

[0165] It is obvious from the above description that the performance recovery method of the fuel cell stack according to one aspect of the present disclosure can accurately judge whether the stack is in a state where the stack performance recovery operation can be performed and whether the vehicle is in a state where the stack performance recovery operation can be performed, thereby appropriately ensuring the performance recovery operation time during vehicle driving, being able to more effectively perform voltage scanning and stack performance recovery, and being able to suppress irreversible degradation of the fuel cell stack, thereby improving the durability of the fuel cell stack.

[0166] The present disclosure has been described in detail with reference to its preferred embodiments. However, it will be appreciated by those skilled in the art that these embodiments may be modified without departing from the principles and spirit of the present disclosure, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for restoring the performance of a fuel cell stack in a fuel cell system of a vehicle, comprising: determining, by a controller, whether the fuel cell stack is in a state where a stack performance recovery operation can be performed based on information collected from the vehicle using a predetermined stack state determination standard; determining, by the controller, based on operating information of the fuel cell system, whether the vehicle is in a state where the stack performance recovery operation can be performed; as well as When it is determined by the controller that the fuel cell stack is in a state where the stack performance recovery operation can be performed and the vehicle is in a state where the stack performance recovery operation can be performed, the stack performance recovery operation is performed. Wherein, the method further comprises: When it is determined by the controller that the fuel cell stack is in a state where the stack performance recovery operation can be performed, confirming a fuel cell stop entry count; and By the controller, during operation of the fuel cell system, when it is determined that a predetermined condition related to the number of confirmed fuel cell stop entries is satisfied, it is determined whether the vehicle is in a state in which the stack performance recovery operation can be performed, The number of times the fuel cell stops entering is confirmed includes: determining whether the number of times that the stack voltage is equal to or less than a predetermined voltage reference value when a fuel cell stop occurs within a predetermined time during operation of the fuel cell system is less than a first predetermined number; and When the number of times the stack voltage is equal to or less than the voltage reference value is less than the first predetermined number, it is determined that the condition related to the number of times the fuel cell stop entry is confirmed is satisfied.

2. The method according to claim 1, wherein Determining whether the fuel cell stack is in a state where a stack performance recovery operation can be performed includes: calculating, during travel of the vehicle and operation of the fuel cell system, a cumulative travel distance obtained by accumulating vehicle travel distances when an output of the fuel cell stack is equal to or greater than a predetermined first output reference value; comparing the determined cumulative travel distance with a distance reference value serving as a stack state determination criterion; and When the determined cumulative running distance is greater than the distance reference value, it is determined that the fuel cell stack is in a state in which the stack performance recovery operation can be performed.

3. The method according to claim 1, wherein Determining whether the fuel cell stack is in a state where a stack performance recovery operation can be performed includes: calculating, during vehicle travel and operation of the fuel cell system, an integrated value of a stack current obtained by integrating a current output from the fuel cell stack, and calculating a cumulative travel distance obtained by accumulating vehicle travel distances when an output of the fuel cell stack is equal to or greater than a predetermined first output reference value; comparing the calculated integrated value of the stack current with a current integrated reference value as a stack state judgment standard, and comparing the judged cumulative running distance with a distance reference value as a stack state judgment standard; and When the calculated integrated value of the stack current is greater than the current integrated reference value or when the calculated cumulative running distance is greater than the distance reference value, it is determined that the fuel cell stack is in a state where the stack performance recovery operation can be performed.

4. The method according to claim 1, wherein Determining whether the vehicle is in a state where the stack performance recovery operation can be performed includes: Whether the vehicle is in a state where the stack performance recovery operation can be performed is determined based on whether the vehicle is in a running state, the charge state (SOC) and dischargeable power of a battery connected to a drive motor to supply power to the drive motor, and a stack required output.

5. The method according to claim 4, wherein Under the conditions that the vehicle is in a running state, the SOC of the battery is equal to or greater than a predetermined first SOC reference value, the dischargeable power of the battery is equal to or greater than a predetermined first power reference value, and the stack required output is less than a predetermined second output reference value, The controller determines that the vehicle is in a state in which the stack performance recovery operation can be performed.

6. The method according to claim 4, wherein: Under the condition that the SOC of the battery is equal to or greater than a predetermined second SOC reference value when the vehicle is in an ignition-off state and not in a driving state, The controller determines that the vehicle is in a state where a stack performance recovery operation can be performed.

7. The method according to claim 1, wherein Executing the heap performance recovery operation includes: switching the driving mode of the vehicle to a battery driving mode, in which the vehicle drives a driving motor using the charged power of the battery; closing a main relay that selectively connects the fuel cell stack to a main bus terminal and is installed on an output side of the fuel cell stack; and Operation of an electric load device connected to the fuel cell stack is controlled to sweep a voltage of the fuel cell stack to restore performance of the fuel cell stack.

8. The method according to claim 7, wherein: The electric load device comprises: COD heaters, which heat the stack coolant; and An air compressor supplies air serving as an oxidizing gas to the fuel cell stack.

9. The method according to claim 8, wherein During the stack performance recovery operation, The controller turns on the COD heater to scan the voltage of the fuel cell stack, performs cooling control of the COD heater using the stack coolant, and performs on / off control of the air compressor, wherein the air compressor is controlled to be alternately turned on and off.

10. The method according to claim 1, further comprising: determining, by the controller, during the stack performance recovery operation, whether a predetermined stack performance recovery operation interruption condition is satisfied; By the controller, when it is determined that the stack performance recovery operation interruption condition is satisfied, determining whether the stack performance recovery operation has been completed; as well as When it is determined by the controller that the stack performance recovery operation has not been completed, the stack status determination standard is changed and the stack performance recovery operation is ended.

11. The method according to claim 10, wherein: Determining whether a predetermined heap performance recovery operation interruption condition is met includes: During the stack performance recovery operation, when at least one of the conditions that the stack required output is less than a predetermined third output reference value, the charge state of a battery connected to a drive motor to supply power to the drive motor, i.e., the SOC, is less than a predetermined third SOC reference value, and the dischargeable power of the battery is less than a second power reference value is satisfied, it is determined that the stack performance recovery operation interruption condition is satisfied.

12. The method according to claim 10, wherein: During the stack performance recovery operation, when the number of executions of the on / off control of the air compressor for scanning the voltage of the fuel cell stack is less than a second predetermined number, The controller determines that the stack performance recovery operation has not been completed.

13. The method according to claim 10, wherein: When it is determined that the heap performance recovery operation has been completed, The controller ends the stack performance recovery operation without changing the stack state determination criterion.

14. The method according to claim 13, wherein During the stack performance recovery operation, when the number of executions of the on / off control of the air compressor for scanning the voltage of the fuel cell stack reaches a second predetermined number, The controller determines that the stack performance recovery operation has been completed.

15. The method according to claim 14, further comprising: By the controller, when it is determined that the stack performance recovery operation interruption condition is not satisfied, determining whether the stack performance recovery operation has been completed; When it is determined by the controller that the stack performance recovery operation has not been completed, maintaining the stack performance recovery operation; as well as When it is determined by the controller that the stack performance recovery operation has been completed, the stack performance recovery operation is ended.

16. The method according to claim 15, wherein During the stack performance recovery operation, when the number of executions of the on / off control of the air compressor reaches the second predetermined number, The controller determines that the stack performance recovery operation has been completed.

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